Translucent paper



Patented Apr. 9, 1935 UNITED STATES .TRANSLUCENT PAPER Paul BallingerDavidson, Pittsburgh, Pa.

' No Drawing. 1 Application November 2, 1933, Serial No. 696,411

- 3 Claims. (01. 91-68) This invention relates to paper-making, andconsists both in method and in product. In the practice of the methodthe paper is rendered translucent and rendered serviceable in new fieldsof use.

Paper in the ordinary meaning of the word is a thin and coherent sheetof cellulose fiber. Vegetable parchment is produced by the long-knownprocess of treating paper with sulphuric acid. The effect of the acid isto swell the fibers of cellulose to the point of producing a gelatinousmass. The process is arrested by washing with water; the gelatinouscellulose, precipitated in the still remaining fibers of the body, actsas a cementing material; the substance of the sheet is rendered morenearly continuous; and, in consequence, the sheet manifests theproperties of translucence, waterproofness, and grease-proofness whichare characteristic of parchment.

The method of the present invention, unlike the sulphuric-acid methodwhose essential character has been indicated, does not involve chemicalchange nor reaction. It is, essentially, a method of impregnation.

In an application for Letters Patent of the United States, filed April30, 1932, Serial No. 608,- have described a treatment of paper byimpregnation, and I have described the impregnating substance to consisttypically of a solution of ethyl or methyl abietate and sucroseoctoacetate in a volatile solvent, and as a volatile solvent I namedpreferably ethylene dichloride.

My further discovery is thatsucrose octoacetate alone, not associatedwith abietate, may be carried in a volatile solvent such as ethylenedichloride, and that when so carried may be caused to impregnate paper,and that, the solvent driven off, the paper will be found to be renderedtranslucent and adequate for many purposes-for example, as tracingpaper.

Other available solvents are acetone, toluene, and rosin spirits. V

softness in greater degree may be imparted to the product by adding tothe solution a fatty acid, preferably a normally solid acid, stearicacid, for instance, or palmitic, in an amount of 5% or less the sucroseoctoacetate.

No particular type of apparatus is necessary for the application-of thisprocess to the paper; any equipment that will impregnate paper with thiscombination of materials and then drive off the excess of solution fromthe treated paper is.

satisfactory. In the practice of the invention the paper may be fioatedonthe solution and the solution allowed to penetrate the paper; and,after this has been accomplished, the excess solution may be removedfrom the paper by means of a scraper bar or the paper may be run betweensqueeze rolls. The paper then is dried. Again, the invention may bepractised by spraying the solution upon the paper, or by completelyimmersing the paper in the solution, as is done in tub-sizing of paper.In any case the excess of solution is removed and the paper is dried.Again, the invention may be practised by passing the untreated paperbetween two rolls, one of which at least carries upon its surface alayer of the solution. Satisfactory applications have been made bypassing the untreated paper between two large steel rolls, one of whichrevolves in a pan containing the solution and carries a layer of thesolution on-its surface. The paper, coming in contact with this layer ofsolution, is immediately impregnated and as it. passes between the rollsthe excess of the solution is 20 squeezed out of the paper. In somecases it may be found advisable to spread a layer of the solution on theupper roll as well as upon the lower, andin this way the paper may bythe two rolls be impregnated from both sides. the parchmentizing ofthepaper may in thiscase be regulated by the degree to which the solutionis diluted with the solvent and, to some extent, by the pressure appliedto the rolls. The drying of the treated paper can be governed to a large30 extent by the proper selection of solvents.

A certain stickiness or tackiness, which otherwise may characterize thepaper, may be eliminated by treating the paper, after impregnation anddrying, by immersion in water. The water.v will dissolve certainincidental impurities, and, these being removed, it will be found thatthe stickiness or tackiness is overcome.

The fiber of paper that has been subjected to the method of theinvention is not altered chemically, and the strength of the paper isnot impaired. Paper that has been subjected to the method of theinvention is receptive of ink, and

may, ashes been said, be used as tracing paper.

It is available, generally, where a translucent paper of relativelygreat strength is desired.

I have further discovered, both with respect to procedure as hereindisclosed and procedure as disclosed in my prior application Serial No.608,;

563, alluded to above, that translucence in greater degree or closerapproach to transparency may be efieqte'd inthis way: Instead ofpreparing the SOIlit'Ol'l, whether of octoacetate'alone as is herecontemplated, or of abietate and octoacetate to- The extent of 25 getheras is in the earlier application disclosed, in

full strength for the purposes in view, a solution of less strength, ofapproximately half full strength, may be Prepared, and with thissolution of half strength the paper may be twice impregnated, allowingit to dry after the first impregnatiom-- If the impregnation be effectedin such two-step manner, it will be found, as I have intimated, that thequality of translucence will be heightened.

I claim as my invention: 7

1. The method herein described of preparing translucent paper whihconsists in impregnating the paper with a solution of sucroseoctoacetate with or without an addition to as much as 5% of a normallysolid fatty acid but otherwise of sucrose octoacetate alone in avolatfle solvent, and driving oil. the solvent.

2. A translucent paper consisting of a paper impregnated with sucroseoctoacetate with or without an addition to as much as 5% oi a normallysolid fatty acid but otherwise of sucrose octoacetate alone.

method herein described of treating pa s to render it translucent whichconsists in impregnating it with a solution of sucrose octoacetate withor without an addition to as much as 5% of a normally solid fatty acidbut otherwise of sucrose octoacetate alone in a volatile solvent,driving ofl the solvent, immersing the paper in water, and finally PAULB; DAVIDSON.

